Clarity and transparency in cosmetic formulations are desired attributes because these features connote freshness, purity, and cleanliness to the cosmetic products. The mass production of clear cosmetic products has been challenging, however, because some of the ingredients employed to promote clarity and transparency have lacked stability when subjected to temperature variations and have lacked stability in storage over time.
Many clear cosmetic formulations have employed soap gel technology. Some of these formulations are described in U.S. Pat. No. 4,759,924 (Luebbe et al). and U.S. Pat. No. 4,226,889 (Yuhas). The reference EP 0 498 488 A2 describes a cosmetic stick with soap partially replaced by polyethylene oxide-polypropylene oxide copolymer. Another formulation with a soap gelling agent is described in WO 96/37186. This formulation describes clarifying agents such as C14-15 Pareth 2.25, C14-15 Pareth 13, Ceteareth-55, PPG-10 cetyl ether, PEG-6 Lauramide, and dimethicone copolymers with ethylene oxide and/or propylene oxide side chains.
Cosmetic sticks generally have a firmness that permits application of a desired amount of active ingredients when the stick is applied over skin. The degree of firmness required depends upon the specific application. The firmness desired has generally been difficult to maintain in transport and storage in environments having high temperatures.